@@ -70,7 +70,7 @@ struct dm_exception_store_type {
* Update the metadata with this exception.
*/
void (*commit_exception) (struct dm_exception_store *store,
- struct dm_exception *e,
+ struct dm_exception *e, int valid,
void (*callback) (void *, int success),
void *callback_context);
@@ -700,7 +700,7 @@ static int persistent_prepare_exception(struct dm_exception_store *store,
}
static void persistent_commit_exception(struct dm_exception_store *store,
- struct dm_exception *e,
+ struct dm_exception *e, int valid,
void (*callback) (void *, int success),
void *callback_context)
{
@@ -709,6 +709,9 @@ static void persistent_commit_exception(struct dm_exception_store *store,
struct core_exception ce;
struct commit_callback *cb;
+ if (!valid)
+ ps->valid = 0;
+
ce.old_chunk = e->old_chunk;
ce.new_chunk = e->new_chunk;
write_exception(ps, ps->current_committed++, &ce);
@@ -52,12 +52,12 @@ static int transient_prepare_exception(struct dm_exception_store *store,
}
static void transient_commit_exception(struct dm_exception_store *store,
- struct dm_exception *e,
+ struct dm_exception *e, int valid,
void (*callback) (void *, int success),
void *callback_context)
{
/* Just succeed */
- callback(callback_context, 1);
+ callback(callback_context, valid);
}
static void transient_usage(struct dm_exception_store *store,
@@ -1436,8 +1436,9 @@ static void __invalidate_snapshot(struct dm_snapshot *s, int err)
dm_table_event(s->ti->table);
}
-static void pending_complete(struct dm_snap_pending_exception *pe, int success)
+static void pending_complete(void *context, int success)
{
+ struct dm_snap_pending_exception *pe = context;
struct dm_exception *e;
struct dm_snapshot *s = pe->snap;
struct bio *origin_bios = NULL;
@@ -1508,24 +1509,13 @@ out:
free_pending_exception(pe);
}
-static void commit_callback(void *context, int success)
-{
- struct dm_snap_pending_exception *pe = context;
-
- pending_complete(pe, success);
-}
-
static void complete_exception(struct dm_snap_pending_exception *pe)
{
struct dm_snapshot *s = pe->snap;
- if (unlikely(pe->copy_error))
- pending_complete(pe, 0);
-
- else
- /* Update the metadata if we are persistent */
- s->store->type->commit_exception(s->store, &pe->e,
- commit_callback, pe);
+ /* Update the metadata if we are persistent */
+ s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
+ pending_complete, pe);
}
/*
This is a note to let you know that I have just added a patch titled dm snapshot: fix hung bios when copy error occurs to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt24. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ---8<------------------------------------------------------------ From e33972a9b5e6a1ab92258308215044bb81e159a1 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka@redhat.com> Date: Fri, 8 Jan 2016 19:07:55 -0500 Subject: dm snapshot: fix hung bios when copy error occurs commit 385277bfb57faac44e92497104ba542cdd82d5fe upstream. When there is an error copying a chunk dm-snapshot can incorrectly hold associated bios indefinitely, resulting in hung IO. The function copy_callback sets pe->error if there was error copying the chunk, and then calls complete_exception. complete_exception calls pending_complete on error, otherwise it calls commit_exception with commit_callback (and commit_callback calls complete_exception). The persistent exception store (dm-snap-persistent.c) assumes that calls to prepare_exception and commit_exception are paired. persistent_prepare_exception increases ps->pending_count and persistent_commit_exception decreases it. If there is a copy error, persistent_prepare_exception is called but persistent_commit_exception is not. This results in the variable ps->pending_count never returning to zero and that causes some pending exceptions (and their associated bios) to be held forever. Fix this by unconditionally calling commit_exception regardless of whether the copy was successful. A new "valid" parameter is added to commit_exception -- when the copy fails this parameter is set to zero so that the chunk that failed to copy (and all following chunks) is not recorded in the snapshot store. Also, remove commit_callback now that it is merely a wrapper around pending_complete. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/md/dm-exception-store.h | 2 +- drivers/md/dm-snap-persistent.c | 5 ++++- drivers/md/dm-snap-transient.c | 4 ++-- drivers/md/dm-snap.c | 20 +++++--------------- 4 files changed, 12 insertions(+), 19 deletions(-)